The invention relates to a baffle and a method and apparatus for supporting a plurality of tubes. In another aspect the invention relates to heat exchangers such as shell and tube heat exchangers and to a method and apparatus to radially support the tubes in such heat exchangers.
Heat transfer is an important part of any process. As is well known, an indirect transfer of heat from one medium to another is usually accomplished by the use of heat exchangers of which there are many types. For example, there are double pipe, shell and tube, plate heat exchangers and others. Indeed, the art of heat exchanger design is developed to a very high degree; however, there is still room for improvement in a number of areas, such as reducing pressure drop, increasing overall heat transfer coefficients, reducing fouling, and in heat exchangers utilizing a tube bundle, such as the shell and tube heat exchangers, improving tube support. In many instances the tubes in a shell and tube heat exchanger prematurely fail because the tubes vibrate or rub against one another or other parts of the heat exchanger, such as for example, a baffle or the shell.
The art has heretofore recognized the need for tube support.
Plate type baffles have been used in heat exchangers for many years. Such baffles provide support for the tubes at least to some degree. The double segmental plate-baffle heat exchanger is well known to those skilled in the art, and although heat exchangers using plate type baffles were a relatively early development in heat exchanger design, such exchangers are still widely used today. In most plate type baffle heat exchangers the passages in the plate baffles through which the tubes pass are slightly larger in diameter than the outside diameter of the tubes in order to facilitate construction of the exchanger, and as a result vibration of the tubes can and does occur which frequently results in premature tube failure.
U.S. Pat. No. 2,018,037, issued to Everett Norman Sieder on Oct. 22, 1935, describes a heat exchanger having a supported tube bundle in which a plurality of bars or rods is disposed in the lanes between tube rows. A bar or rod is disposed in each lane and affixed to a ring surrounding the tube bundle so that the bars form a series of parallel chords positioned in a plane perpendicular to the longitudinal axis of the tube bundle. When viewing a cross section of the longitudinal axis of the bundle as shown in FIGS. 2, 3 and 6 of the patent, a bar is shown in each and every lane. Thus, two groups or pluralities of bars provide radial support for each tube in the tube bundle. Although such a structure provides very good support for the tubes in the tube bundle, it incurs the penalty of a relatively large pressure loss which, besides being wasteful of energy, is usually a higher pressure loss than can be tolerated. In fact, even though this patented design is some thirty years old, it is not well accepted by industry as evidenced by the fact that it is rarely if ever used.
A tube support which is used and which does provide a low pressure drop is that described in U.S. Pat. No. 3,708,142, issued Jan. 2, 1973 to the same inventor as the inventor of the present invention. The design of the present invention provides a substantial improvement in heat transfer coefficients and fouling resistance at a relatively small increase in pressure drop as compared to the earlier invention referred to above. Thus, although the pressure drop is generally lower for an exchanger constructed in accordance with U.S. Pat. No. 3,708,142, as compared to an exchanger constructed in accordance with the present invention, the present invention provides a better overall compromise when both the pressure drop and the heat transfer coefficient are considered. In addition, tube bundles supported in accordance with the present invention are somewhat cheaper to fabricate in some instances as compared to those of the earlier invention.
It is emphasized that the present invention is a very significant breakthrough in heat exchanger design because supporting a tube bundle in accordance with the present invention limits tube failure due to such things as vibration, improves the overall heat transfer coefficient as compared to prior art heat exchangers and at the same time reduces the pressure drop as compared to the plate type baffle heat exchangers well known in the art. Also, heat exchangers employing the inventive baffles and supporting apparatus are economically competitive with heat exchangers of the prior art and at the same time provide better overall performance.
An object of the invention is to support tubes of a tube bundle.
Another object of the invention is to lower the pressure drop on the shell side of a shell and tube heat exchanger and maintain a higher heat transfer coefficient as compared to heat exchangers known in the art.
Another object of the invention is to protect the tubes in a tube bundle from failure due to vibration.
Another object of the invention is to reduce the external fouling of tube bundles such as the fouling on the shell side of a shell and tube heat exchanger and the consequent loss of heat transfer capability.
Still another object of the invention is to provide a tube support to substantially reduce tube failure in a tube bundle and at the same time improve heat transfer coefficients and reduce the pressure drop on the shell side of a shell and tube heat exchanger.
Other objects, aspects and advantages of the invention will be apparent to those skilled in the art upon a study of the specification and drawings.